<!DOCTYPE html>
<html lang="en-US">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <title>Promise实现动态红绿灯切换 | Jaho’s Blog</title>
    <meta name="generator" content="VuePress 1.8.0">
    <link rel="icon" href="/favicon.ico">
    <link rel="manifest" href="/manifest.json">
    <meta name="description" content="记录日常学习工作">
    
    <link rel="preload" href="/assets/css/0.styles.5b8fe0a4.css" as="style"><link rel="preload" href="/assets/js/app.6514719e.js" as="script"><link rel="preload" href="/assets/js/2.ea114ffb.js" as="script"><link rel="preload" href="/assets/js/56.baf60ba5.js" as="script"><link rel="preload" href="/assets/js/4.e093c564.js" as="script"><link rel="prefetch" href="/assets/js/10.13203aa5.js"><link rel="prefetch" href="/assets/js/11.099868c4.js"><link rel="prefetch" href="/assets/js/12.c8365e17.js"><link rel="prefetch" href="/assets/js/13.89751e7c.js"><link rel="prefetch" href="/assets/js/14.31f563eb.js"><link rel="prefetch" href="/assets/js/15.08b381b6.js"><link rel="prefetch" href="/assets/js/16.1a3867de.js"><link rel="prefetch" href="/assets/js/17.7dd4e0c6.js"><link rel="prefetch" href="/assets/js/18.907c4597.js"><link rel="prefetch" href="/assets/js/19.fac8aa1a.js"><link rel="prefetch" href="/assets/js/20.73fe0e75.js"><link rel="prefetch" href="/assets/js/21.5c50aa1c.js"><link rel="prefetch" href="/assets/js/22.83d03663.js"><link rel="prefetch" href="/assets/js/23.061e7ac0.js"><link rel="prefetch" href="/assets/js/24.cc7e9011.js"><link rel="prefetch" href="/assets/js/25.fa6c7aef.js"><link rel="prefetch" href="/assets/js/26.39392f70.js"><link rel="prefetch" href="/assets/js/27.204436be.js"><link rel="prefetch" href="/assets/js/28.3f54c157.js"><link rel="prefetch" href="/assets/js/29.799d048c.js"><link rel="prefetch" href="/assets/js/3.6c5d6214.js"><link rel="prefetch" href="/assets/js/30.deed02f3.js"><link rel="prefetch" href="/assets/js/31.5916873b.js"><link rel="prefetch" href="/assets/js/32.b0634144.js"><link rel="prefetch" href="/assets/js/33.734675b8.js"><link rel="prefetch" href="/assets/js/34.20404dc4.js"><link rel="prefetch" href="/assets/js/35.d93b829f.js"><link rel="prefetch" href="/assets/js/36.b0692d8d.js"><link rel="prefetch" href="/assets/js/37.3dffa306.js"><link rel="prefetch" href="/assets/js/38.04649a97.js"><link rel="prefetch" href="/assets/js/39.7dfcdc32.js"><link rel="prefetch" href="/assets/js/40.04914511.js"><link rel="prefetch" href="/assets/js/41.ced85449.js"><link rel="prefetch" href="/assets/js/42.72739213.js"><link rel="prefetch" href="/assets/js/43.de1cff16.js"><link rel="prefetch" href="/assets/js/44.48e301ae.js"><link rel="prefetch" href="/assets/js/45.870a7650.js"><link rel="prefetch" href="/assets/js/46.657f15b8.js"><link rel="prefetch" href="/assets/js/47.3df1bfdb.js"><link rel="prefetch" href="/assets/js/48.f4e4e774.js"><link rel="prefetch" href="/assets/js/49.632bf611.js"><link rel="prefetch" href="/assets/js/5.6531e181.js"><link rel="prefetch" href="/assets/js/50.a8018493.js"><link rel="prefetch" href="/assets/js/51.cb424f59.js"><link rel="prefetch" href="/assets/js/52.a9f595dc.js"><link rel="prefetch" href="/assets/js/53.cf8a9ec0.js"><link rel="prefetch" href="/assets/js/54.46d774a3.js"><link rel="prefetch" href="/assets/js/55.3574f9b8.js"><link rel="prefetch" href="/assets/js/57.af42b559.js"><link rel="prefetch" href="/assets/js/58.9300cb59.js"><link rel="prefetch" href="/assets/js/6.00f437ec.js"><link rel="prefetch" href="/assets/js/7.58ac7166.js"><link rel="prefetch" href="/assets/js/8.1b9c5002.js"><link rel="prefetch" href="/assets/js/9.5c076362.js">
    <link rel="stylesheet" href="/assets/css/0.styles.5b8fe0a4.css">
  </head>
  <body>
    <div id="app" data-server-rendered="true"><div class="theme-container"><header class="navbar"><div class="sidebar-button"><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" role="img" viewBox="0 0 448 512" class="icon"><path fill="currentColor" d="M436 124H12c-6.627 0-12-5.373-12-12V80c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12z"></path></svg></div> <a href="/" class="home-link router-link-active"><img src="/logo.png" alt="Jaho’s Blog" class="logo"> <span class="site-name can-hide">Jaho’s Blog</span></a> <div class="links"><div class="search-box"><input aria-label="Search" autocomplete="off" spellcheck="false" value=""> <!----></div> <nav class="nav-links can-hide"><div class="nav-item"><a href="/posts/" class="nav-link router-link-active">
  技术博客
</a></div> <a href="https://juejin.cn/user/26836627369806" target="_blank" rel="noopener noreferrer" class="repo-link">
    个人主页
    <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav></div></header> <div class="sidebar-mask"></div> <aside class="sidebar"><nav class="nav-links"><div class="nav-item"><a href="/posts/" class="nav-link router-link-active">
  技术博客
</a></div> <a href="https://juejin.cn/user/26836627369806" target="_blank" rel="noopener noreferrer" class="repo-link">
    个人主页
    <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav>  <ul class="sidebar-links"><li><a href="/posts/" aria-current="page" class="sidebar-link">写在前面</a></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading open"><span>工作问题解决</span> <span class="arrow down"></span></p> <ul class="sidebar-links sidebar-group-items"><li><a href="/posts/项目问题解决/vuevite.html" class="sidebar-link">vue3+vite用proxy解决跨域及proxy原理解析</a></li><li><a href="/posts/项目问题解决/大文件.html" class="sidebar-link">大文件切片上传和断点续传</a></li><li><a href="/posts/项目问题解决/代码优化.html" class="sidebar-link">实际工作中代码优化</a></li><li><a href="/posts/项目问题解决/组件问题.html" class="sidebar-link">解决组件传值问题</a></li><li><a href="/posts/项目问题解决/动态组件.html" class="sidebar-link">动态组件实践</a></li><li><a href="/posts/项目问题解决/大屏.html" class="sidebar-link">大屏九宫格视频</a></li><li><a href="/posts/项目问题解决/滚动.html" class="sidebar-link">Vue中Element表单定位滚动到校验错误位置</a></li><li><a href="/posts/项目问题解决/红绿灯.html" class="active sidebar-link">Promise实现动态红绿灯切换</a></li><li><a href="/posts/项目问题解决/懒加载.html" class="sidebar-link">实现元素懒加载</a></li><li><a href="/posts/项目问题解决/小程序组件.html" class="sidebar-link">微信小程序封装组件</a></li><li><a href="/posts/项目问题解决/axios.html" class="sidebar-link">项目中对axios的整体封装</a></li><li><a href="/posts/项目问题解决/docker.html" class="sidebar-link">docker实践(附windows安装下载教程)</a></li><li><a href="/posts/项目问题解决/eltable.html" class="sidebar-link">el-table自定义表头及无数据状态</a></li><li><a href="/posts/项目问题解决/gojs.html" class="sidebar-link">gojs入门学习</a></li><li><a href="/posts/项目问题解决/react踩坑.html" class="sidebar-link">React踩坑</a></li><li><a href="/posts/项目问题解决/小程序踩坑.html" class="sidebar-link">小程序踩坑</a></li></ul></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>JavaScript</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Css</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Nodejs</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Vue</span> <span class="arrow right"></span></p> <!----></section></li><li><section class="sidebar-group collapsable depth-0"><p class="sidebar-heading"><span>Git</span> <span class="arrow right"></span></p> <!----></section></li></ul> </aside> <main class="page"> <div class="theme-default-content content__default"><h1 id="promise实现动态红绿灯切换"><a href="#promise实现动态红绿灯切换" class="header-anchor">#</a> Promise实现动态红绿灯切换</h1> <p>前段时间写了一个Promise实现红绿灯的操作，但是只有代码没有直观的样例显示，趁着这次码上掘金活动，将Promise红绿灯的操作放到dom中来进行具体的可视化实现，采用的原理还是之前的Promise和async、await的写法一直，通过事件循环的方式来对红绿灯进行颜色的切换，同时加入了倒计时的数字，更新了一下版本。</p> <p>文章的内容不多，欢迎大家阅读和批评指正。</p> <div class="language-js extra-class"><pre class="language-js"><code><span class="token operator">&lt;</span>div <span class="token keyword">class</span><span class="token operator">=</span><span class="token string">&quot;light&quot;</span><span class="token operator">&gt;</span>
      <span class="token operator">&lt;</span>div <span class="token operator">:</span><span class="token keyword">class</span><span class="token operator">=</span><span class="token string">&quot;['ll' ,lightColor=='red'?'l1':'']&quot;</span><span class="token operator">&gt;</span><span class="token punctuation">{</span><span class="token punctuation">{</span>lightColor<span class="token operator">==</span><span class="token string">'red'</span><span class="token operator">?</span>index<span class="token operator">:</span><span class="token string">''</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token operator">&lt;</span><span class="token operator">/</span>div<span class="token operator">&gt;</span>
      <span class="token operator">&lt;</span>div <span class="token operator">:</span><span class="token keyword">class</span><span class="token operator">=</span><span class="token string">&quot;['ll' ,lightColor=='green'?'l2':'']&quot;</span><span class="token operator">&gt;</span><span class="token punctuation">{</span><span class="token punctuation">{</span>lightColor<span class="token operator">==</span><span class="token string">'green'</span><span class="token operator">?</span>index<span class="token operator">:</span><span class="token string">''</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token operator">&lt;</span><span class="token operator">/</span>div<span class="token operator">&gt;</span>
      <span class="token operator">&lt;</span>div <span class="token operator">:</span><span class="token keyword">class</span><span class="token operator">=</span><span class="token string">&quot;['ll' ,lightColor=='yellow'?'l3':'']&quot;</span><span class="token operator">&gt;</span><span class="token punctuation">{</span><span class="token punctuation">{</span>lightColor<span class="token operator">==</span><span class="token string">'yellow'</span><span class="token operator">?</span>index<span class="token operator">:</span><span class="token string">''</span><span class="token punctuation">}</span><span class="token punctuation">}</span><span class="token operator">&lt;</span><span class="token operator">/</span>div<span class="token operator">&gt;</span>
    <span class="token operator">&lt;</span><span class="token operator">/</span>div<span class="token operator">&gt;</span>
</code></pre></div><p>先放置我们的div，给三个灯加上各自的样式，Js中会通过循环改变lightColor的值从而让各个灯去切换不同的颜色，同时会在各个灯中写入一个倒计时的样式，</p> <div class="language-js extra-class"><pre class="language-js"><code>  <span class="token operator">&lt;</span>script<span class="token operator">&gt;</span>
  <span class="token keyword">import</span> <span class="token punctuation">{</span> defineComponent<span class="token punctuation">,</span> ref <span class="token punctuation">}</span> <span class="token keyword">from</span> <span class="token string">'vue'</span><span class="token punctuation">;</span>
  
  <span class="token keyword">export</span> <span class="token keyword">default</span> <span class="token function">defineComponent</span><span class="token punctuation">(</span><span class="token punctuation">{</span>
    <span class="token function">setup</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
      <span class="token keyword">const</span> count <span class="token operator">=</span> <span class="token function">ref</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
      <span class="token keyword">function</span> <span class="token function">addCount</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        count<span class="token punctuation">.</span>value <span class="token operator">+=</span> <span class="token number">1</span><span class="token punctuation">;</span>
      <span class="token punctuation">}</span>
      <span class="token keyword">let</span> lightColor <span class="token operator">=</span> <span class="token function">ref</span><span class="token punctuation">(</span><span class="token string">''</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
      <span class="token keyword">let</span> index <span class="token operator">=</span> <span class="token function">ref</span><span class="token punctuation">(</span><span class="token number">0</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
      <span class="token keyword">let</span> lightTimer 
      <span class="token function">start</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
      <span class="token keyword">async</span> <span class="token keyword">function</span> <span class="token function">start</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
        <span class="token keyword">await</span> <span class="token function">light</span><span class="token punctuation">(</span><span class="token string">'red'</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">)</span>
        <span class="token keyword">await</span> <span class="token function">light</span><span class="token punctuation">(</span><span class="token string">'green'</span><span class="token punctuation">,</span><span class="token number">5</span><span class="token punctuation">)</span>
        <span class="token keyword">await</span> <span class="token function">light</span><span class="token punctuation">(</span><span class="token string">'yellow'</span><span class="token punctuation">,</span><span class="token number">3</span><span class="token punctuation">)</span>
        <span class="token function">start</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
      <span class="token punctuation">}</span>
      <span class="token keyword">function</span> <span class="token function">light</span><span class="token punctuation">(</span><span class="token parameter">color<span class="token punctuation">,</span>timer</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
        lightColor<span class="token punctuation">.</span>value <span class="token operator">=</span> color
        index<span class="token punctuation">.</span>value <span class="token operator">=</span> timer
        <span class="token keyword">return</span> <span class="token keyword">new</span> <span class="token class-name">Promise</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token parameter">res<span class="token punctuation">,</span>rej</span><span class="token punctuation">)</span><span class="token operator">=&gt;</span><span class="token punctuation">{</span>
            index<span class="token punctuation">.</span>value <span class="token operator">=</span> timer<span class="token operator">--</span>
            lightTimer <span class="token operator">=</span> <span class="token function">setInterval</span><span class="token punctuation">(</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">=&gt;</span> <span class="token punctuation">{</span>
                console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>timer<span class="token punctuation">)</span>
                index<span class="token punctuation">.</span>value <span class="token operator">=</span> timer<span class="token operator">--</span>
                <span class="token keyword">if</span><span class="token punctuation">(</span>index<span class="token punctuation">.</span>value<span class="token operator">==</span><span class="token operator">-</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">{</span>
                    <span class="token function">clearInterval</span><span class="token punctuation">(</span>lightTimer<span class="token punctuation">)</span>
                    <span class="token function">res</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
                <span class="token punctuation">}</span>
            <span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token number">1000</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
                <span class="token comment">// setTimeout(()=&gt;{</span>
                <span class="token comment">// },timer*1000)</span>
        <span class="token punctuation">}</span><span class="token punctuation">)</span>
      <span class="token punctuation">}</span>
      <span class="token keyword">return</span> <span class="token punctuation">{</span>
        count<span class="token punctuation">,</span>
        addCount<span class="token punctuation">,</span>
        lightColor<span class="token punctuation">,</span>
        index
      <span class="token punctuation">}</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span><span class="token punctuation">,</span>
  <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token operator">&lt;</span><span class="token operator">/</span>script<span class="token operator">&gt;</span>
</code></pre></div><p>js部分还是按照之前的async和await的写法来进行切换操作，原理就是在各个await中返回我们的Promise，按照事件循环的原理，JS遇到await中会停止后续代码的进行，需要当其中的Promise执行完成并且返回一个状态的时候才会执行后续的代码</p> <p>这里我们在Promise执行前的时候，先对Promise加入颜色的切换，然后写入初始的倒计时，接着发出我们的定时器，定时器的时间按照传入的延时进行操作，定时器结束后返回状态，并且在定时器中加入interval来对倒计时进行实现，每一秒减少，定时器结束后返回一个resolved，await会跳出，执行下一行的代码，也就是下一个awiat。</p> <p>当我们的红绿灯切换一轮之后，继续调用start函数，其实就是通过调用自己来进行自动的下一轮红绿灯的切换。这样就达到了自动切换的效果。</p></div> <footer class="page-edit"><!----> <div class="last-updated"><span class="prefix">上次更新:</span> <span class="time">2023-01-04 10:56:12</span></div></footer> <div class="page-nav"><p class="inner"><span class="prev">
      ←
      <a href="/posts/项目问题解决/滚动.html" class="prev">
        Vue中Element表单定位滚动到校验错误位置
      </a></span> <span class="next"><a href="/posts/项目问题解决/懒加载.html">
        实现元素懒加载
      </a>
      →
    </span></p></div> </main></div><div class="global-ui"><!----><!----></div></div>
    <script src="/assets/js/app.6514719e.js" defer></script><script src="/assets/js/2.ea114ffb.js" defer></script><script src="/assets/js/56.baf60ba5.js" defer></script><script src="/assets/js/4.e093c564.js" defer></script>
  </body>
</html>
